Rationale: Tumor necrosis factor receptor-associated factors (TRAFs) are cytoplasmic adaptor proteins for the TNF/interleukin-1/Toll-like receptor superfamily. Ligands of this family comprise multiple important cytokines such as TNF␣, CD40L, and interleukin-1␤ that promote chronic inflammatory diseases such as atherosclerosis. We recently reported overexpression of TRAF5 in murine and human atheromata and that TRAF5 promotes inflammatory functions of cultured endothelial cells and macrophages.Objective: This study tested the hypothesis that TRAF5 modulates atherogenesis in vivo. Methods and Results: Surprisingly, TRAF5؊/؊ /LDLR ؊/؊ mice consuming a high-cholesterol diet for 18 weeks developed significantly larger atherosclerotic lesions than did TRAF5 ؉/؉ /LDLR ؊/؊ controls. Plaques of TRAF5-deficient animals contained more lipids and macrophages, whereas smooth muscle cells and collagen remained unchanged. Deficiency of TRAF5 in endothelial cells or in leukocytes enhanced adhesion of inflammatory cells to the endothelium in dynamic adhesion assays in vitro and in murine vessels imaged by intravital microscopy in vivo. TRAF5 deficiency also increased expression of adhesion molecules and chemokines and potentiated macrophage lipid uptake and foam cell formation. These findings coincided with increased activation of JNK and appeared to be independent of TRAF2. Finally, patients with stable or acute coronary heart disease had significantly lower amounts of TRAF5 mRNA in blood compared with healthy controls. Key Words: TRAF5 Ⅲ inflammation Ⅲ atherosclerosis Ⅲ monocyte recruitment Ⅲ foam cells A therosclerosis is one of the leading causes of death worldwide. The concept that inflammatory and immunologic mechanisms drive atherogenesis emerged from both extensive laboratory studies and from clinical observations demonstrating associations between biomarkers of inflammation and cardiovascular events. 1,2 These findings have spurred the quest for antiinflammatory or immunomodulatory treatments to fight atherosclerosis and its sequelae. Selective modulation of key signaling pathways may afford a fruitful strategy to achieve that goal. Conclusions:Tumor necrosis factor (TNF) receptor-associated factors (TRAFs) represent important signal transducers for the TNF/ interleukin (IL)-1/Toll-like receptor (TLR) superfamily, several members of which potently promote atherogenesis. We and others found expression of TRAFs in cells typically resident in the atherosclerotic plaques. [3][4][5][6] However, only a few reports have investigated TRAF-dependent functions in the context of vascular disease: TRAF3 and TRAF2 have been implicated in transducing shear stress, 7,8 and Luo et al recently demonstrated that activation of TNFR2 mediates ischemia-induced atherogenesis by inducing TRAF2-dependent survival pathways. 9 Endothelial cells (ECs) and smooth muscle cells from unstable plaque regions of human carotid arteries overexpress TRAF4. 4 TRAF6 promotes neointima formation on balloon injury in the carotid artery of mice as well as deve...

T he metabolic syndrome comprises a cluster of risk factors, including obesity, insulin resistance, hepatic steatosis, and dyslipidemia. It is associated with a variety of cardiovascular diseases such as atherosclerosis, myocardial infarction, and stroke.1 Chronic, low-grade inflammation in key metabolic organs such as the liver and visceral adipose tissue (VAT) Background-Costimulatory cascades such as the CD40L-CD40 dyad enhance immune cell activation and inflammation during atherosclerosis. Here, we tested the hypothesis that CD40 directly modulates traits of the metabolic syndrome in diet-induced obesity in mice. Methods and Results-To induce the metabolic syndrome, wild-type or CD40 −/− mice consumed a high-fat diet for 20 weeks. Unexpectedly, CD40−/− mice exhibited increased weight gain, impaired insulin secretion, augmented accumulation of inflammatory cells in adipose tissue, and enhanced proinflammatory gene expression. This proinflammatory and adverse metabolic phenotype could be transplanted into wild-type mice by reconstitution with CD40-deficient lymphocytes, indicating a major role for CD40 in T or B cells in this context. Conversely, therapeutic activation of CD40 signaling by the stimulating antibody FGK45 abolished further weight gain during the study, lowered glucose levels, improved insulin sensitivity, and suppressed adipose tissue inflammation. Mechanistically, CD40 activation decreased the expression of proinflammatory cytokines in T cells but not in B cells or macrophages. Finally, repopulation of lymphocyte-free Rag1 −/− mice with CD40 −/− T cells provoked dysmetabolism and inflammation, corroborating a protective role of CD40 on T cells in the metabolic syndrome. Finally, levels of soluble CD40 showed a positive association with obesity in humans, suggesting clinical relevance of our findings. Conclusions-We present the surprising finding that CD40 deficiency on T cells aggravates whereas activation of CD40 signaling improves adipose tissue inflammation and its metabolic complications. Therefore, positive modulation of the CD40 pathway might describe a novel therapeutic concept against cardiometabolic disease. T-regulatory (T reg ) cells, CD8 + T cells, and related chemokines and cytokines such as RANTES (regulated on activation normal T cell expressed and secreted) and interferon-γ (IFNγ) colocalize within the inflammatory cell compartment in adipose tissue. 7 In lean adipose tissue, the vast majority of T lymphocytes share features of anti-inflammatory, interleukin (IL)-13-, IL-4-, and IL-10-secreting Th2 or T reg cells. 8In obesity, proinflammatory Th1 cells expressing IFNγ overwhelm Th2 cells.9 Th1 cells, in turn, activate proinflammatory cytokine-secreting macrophages and promote their conversion from M2-like, IL-10-secreting, alternatively activated macrophages to classically activated, M1-like macrophages. 10,11Despite description of the kinetics of cellular infiltration and the associated cytokine/chemokine profiles during the development of obesity, the underlying cause modu...

Objective-Spleen tyrosine kinase (SYK) has come into focus as a potential therapeutic target in chronic inflammatory diseases, such as rheumatoid arthritis and asthma, as well as in B-cell lymphomas. SYK has also been involved in the signaling of immunoreceptors, cytokine receptors, and integrins. We therefore hypothesized that inhibition of SYK attenuates the inflammatory process underlying atherosclerosis and reduces plaque development. Methods and Results-Low-density lipoprotein receptor-deficient mice consuming a high-cholesterol diet supplemented with 2 doses of the orally available SYK inhibitor fostamatinib for 16 weeks showed a dose-dependent reduction in atherosclerotic lesion size by up to 59Ϯ6% compared with the respective controls. Lesions of fostamatinib-treated animals contained fewer macrophages but more smooth muscle cells and collagen-characteristics associated with more stable plaques in humans. Mechanistically, fostamatinib attenuated adhesion and migration of inflammatory cells and limited macrophage survival. Furthermore, fostamatinib normalized high-cholesterol diet-induced monocytosis and inflammatory gene expression. Conclusion-We